1. Field of the Invention
The present invention relates to a recording medium, an apparatus for accessing a recording medium, a method for accessing a recording medium, and a program for executing the method.
2. Description of the Related Art
Recently, as the density and capacity of optical discs are increased, it is important to secure the reliability of the optical. In an optical disc apparatus, adjustment is performed in order to secure the reliability of an optical disc. By adjustment, conditions for recording/reproduction of an optical disc are obtained. The recording/reproduction conditions include a recording power condition indicating an optimum power of a semiconductor laser irradiating an optical disc with laser light when recording data thereonto. The recording power condition is obtained by recording power adjustment.
Japanese Laid-Open Publication No. 4-141827 discloses an exemplary recording power adjustment. According to this technique, adjustment is performed as follows. A signal is recorded into an evaluation track on an optical disc by changing laser light gradually. It is determined whether the recorded signal is normal or abnormal. When the result of the determination is satisfactory, the lowest power is determined within a range in which the recorded signal is determined to be normal.
FIG. 11 shows a conventional recording power adjustment procedure. Hereinafter, the conventional recording power adjustment procedure will be described with reference to FIG. 11.
Step 1101: an adjustment area A is selected by selecting randomly a track for adjusting among evaluation tracks in an optical disc (adjustment area selection). The adjustment area selection procedure will be described elsewhere below.
Step 1102: a recording power for adjustment is determined. For example, at least one recording power is determined for adjustment using the selected track.
Step 1103: data is recorded into the adjustment area A. For example, when a plurality of recording powers are set, the selected adjustment area is divided into a plurality of areas and data is recorded into the areas using the respective different recording powers.
Step 1104: using the recorded areas, the degree of modulation of a reproduced signal is measured. The degree of modulation (modulation degree) is a value indicating the amplitude of a reproduced signal.
Step 1105: an optimum power is calculated based on the measured modulation degrees.
Step 1106: test recording is performed in the selected area using the calculated power.
Step 1107: the error rate of a test recorded area is measured.
Step 1108: it is determined whether or not the measured error rate is within a predetermined range. When it is determined that the error rate is within the predetermined range (YES), the process goes to step 1109. When it is determined that the error rate is not within the predetermined range (NO), the process goes to step 1102. Steps 1102 to 1108 are repeated.
Step 1109: an adjustment resultant power is set and adjustment is ended.
FIG. 12 shows a detailed procedure of the adjustment area selection. Hereinafter, the adjustment area selection procedure (step 1101) will be described step by step with reference to FIG. 12.
Step 1201: an adjustment area is selected at random.
Step 1202: test recording is performed on the selected adjustment area.
Step 1203: the error rate of the test recorded adjustment area is measured.
Step 1204: it is determined whether or not the measured error rate is within a predetermined range.
When it is determined that the error rate is within the predetermined range (YES), the process goes to end. When it is determined that the error rate is not within the predetermined range (NO), the process goes to step 1201 and the adjustment area selection is repeated.
Recording power adjustment is performed every time an optical disc apparatus is started up after an optical disc is loaded into the optical disc apparatus, or alternatively, every time characteristics of an optical disc or an optical disc apparatus are changed by more than a predetermined amount due to a factor, such as a change in temperature or the like.
Recording/reproduction conditions are determined using a drive test area provided in the inner peripheral area of an optical disc. An optical disc apparatus records/reproduces a loaded optical disc under the determined recording/reproduction conditions.
Japanese Laid-Open Publication No. 2000-293859 discloses an exemplary method for recording/reproducing information under predetermined recording/reproduction conditions. In this method, a predetermined optical disc is used for high-speed adjustment. The optical disc includes an area storing identification information about optical disc apparatuses and recording/reproduction conditions for each apparatus. When the identification information of an apparatus for recording or reproduction (herein after referred to as an optical disc apparatus) matches the stored identification information, recording or reproduction is performed using the stored recording/reproduction conditions.
In order to perform adjustment with high precision, it is desirable to select an area having good recording conditions as an adjustment area.
Recently, the capacity and density of optical discs and the speed of recording/reproduction have been further increased. Therefore, it is necessary to reduce the time required to perform adjustment for obtaining recording/reproduction conditions.
The drive test area of an optical disc is limited. Adjustment is required for determination of a recording power condition as well as various other recording/reproduction conditions. Therefore, it is necessary to use the drive test area efficiently.